Methods that enable reuse of recording media such as paper by erasing the color of the toner- or ink-image formed on paper or other recording media are very effective from the viewpoint of environmental protection afforded by reduced amounts of paper or other recording media, and from the economical standpoint.
A decolorizable electrophotographic toner is known that contains a color-forming compound and a color-developing agent, and that can be decolored under heat. In this technique, the color-forming compound and the color-developing agent are incorporated into the toner using a knead pulverization method. The toner in a printed portion can be decolored by heating the printed paper at 100 to 200° C. for about 1 to 3 hours, and the decolored paper can be reused. The technique is outstanding in the sense that it can reduce paper consumption, and can thus contribute to reducing the environmental load.
The inkjet method is a non-electrophotographic image forming method. The characteristic of the inkjet method is that it does not involve heat history for the recording material as in the fusing in the electrophotographic method. The ink jet method is therefore very effective for materials to be erased by heat.
Decolorizable inkjet inks are proposed; however, decoloration is often time consuming, and the color density is not always sufficient.